A conventional bin used for powder or particle material and installed on transporting vehicle is in a form of horizontally arranged cylindrical tank or horizontally arranged double-conical-tank, as shown in FIGS. 1 and 2. FIG. 1 shows a conventional bin in the form of a horizontally arranged cylindrical tank, including cylindrical outer housing part and multiple inner chambers disposed inside said housing part and communicated with each other to accommodate the material therein. A discharging port is disposed in the bottom part of each inner chamber, and the inner chamber further includes inclined sliding plates and a conical bottom part so as to let the material move to the discharging port. Thus, there are lots of cavities, which can not be used for accommodating the material, formed between the outer housing part and the sliding plates as well as the conical bottom part of the inner chamber. Similarly, FIG. 2 shows a conventional bin in the form of a horizontally arranged double-conical-tank, including an outer housing part in a double-conical shape and an inner chamber disposed inside the housing part and used for accommodating the material. The inner chamber includes inclined sliding plates, for directing the material to the discharging port in the bottom part. Likewise, there are lots of cavities, which can not be used for accommodating the material, formed between the outer housing part and the sliding plates of the inner chamber. Due to the presence of such cavities, the material would leak to said cavities once cracks appear in walls of the inner chamber. Consequently, the inner chamber has to be emptied and the leaked material has to be removed during maintenance, and the cracks could be welded only from the inner side of the inner chamber, such that the quality of welding can not be guaranteed and the cost of maintenance is high.
In view of this, the applicant ever developed a new composite bin comprising multiple vertical bin units, each including a cylindrical side wall, an arched top part with a charging port and a conical bottom part with a discharging port. The cylindrical side walls of the adjacent bin units intersect with each other, and the bin units are internally communicated. Such a composite bin does not include outer housing part as the conventional composite bin, and thus if cracks appeared in the bin unit, the cracks could be welded from either the inside or outside, so that the quality of welding can be guaranteed and the maintenance becomes relatively simple. The disclosure of such a composite bin can be found in the applicant's former Chinese patents for design, 200330103801.3, 200530014868.9, 200530014180.0, 200630000218.3, and 200630000219.8 and a Chinese patent for utility model 2003201220330.
FIG. 3 shows a perspective view of the prior composite bin with no outer housing part that had been developed by the applicant. FIG. 4 shows the cross section view of the composite bin of FIG. 3 taken along the horizontal plane. None of the side walls of the bin units has a complete cylindrical shape due to the intersection between the adjacent bin units in the composite bin shown in said figures. The intersection portion of the adjacent bin units forms a concave part in the cross section shown in the figures. During manufacturing, extra materials for forming the surface of the bin should be needed to form this concave part, which could provide no contribution to the inner volume of the composite bin, and this in turn causes a waste of the surface material. Considering the efficiency of the surface material for forming the inner volume, it is necessary to improve the structure of this part.